Moulding hollow glass articles



May 25, 1965 Filed Nov. 10, 1959 J. E. WlLCOCK 3,185,558

MOULDING HOLLOW GLASS ARTICLES 3 Sheets-Sheet 1 a g g pflllpenlor By 0M)4, g 4;, ,2! I /\j +4 Allorfieys May 25, 1965 J. E. WiLCOCK MOULDING-HOLLOW GLASS ARTICLES 3 Sheets-Sheet 2 Filed Nov. 10. 1959 Ma 25, 19655 J. E. WILCOCK 3,185,558

MOULDING HOLLOW GLASS ARTICLES Filed Nov. 10, 1959 3 Sheets-Sheet 53,185,558 MOULDING HOLLOW GLASS ARTICLES John Edward Wilcock, St.Helens, England, assignor to Pilkington Brothers Limited, Liverpool,England, a corporation of Great Britain Filed Nov. 10, 1959, Ser. No.852,120 Claims priority, application GreatBritain, Nov. 17, 1958,

36,965/58 2 Claims. (Cl. 65-76) This invention relates to the mouldingofhollow glass articles, and in particular to a method of and apparatusperiod of dwell during which the pressure member must be held in itsmoulding position until the thicker parts have stiffened sufficientlytohold their shape, the thinner parts will have cooled until they havestiffened to such a degree that they cannot continue cooling withoutcracking on account of the presence of that part of the pressure memberwhich has formed them and which is itself becoming hotter and expandingand is all the more opposing the contraction of the thinner parts.

Moreover if the thinner part of a moulded article is its hollow part itwill be entered first by the pressure member, and by its quick coolingin contact with the pressure member before the pressure member hascompleted the further movement which it must make to mould the thickerparts, the thinner part will become too stiff to accomodate that furthermovement and will crack.

It is a main object of the present invention to overcome the first ofthese difficulties by moulding a hollow glass article in such a way thatcontraction of thethinner parts as they cool is not opposed while thethicker parts are becoming stiffened sufficiently to hold their shape.

A further object of the invention is to overcome the second ofthesedifficulties by forming the thinner parts of an article before thethicker parts are formed so that no flow of glass needs to be enforcedin the thinner parts of an article during the forming of the thickerparts.

According to the present invention there is provided a method ofmoulding a hollow glass article comprising two contiguous inner andouter parts one of which is thinner than the other,consisting incharging a mould with 'a requisitequantity of molten glass,applyingmoulding pressure to the glass tomould the inner part thenapplying moulding pressure to mould the outer part, withdrawing themoulding pressure which has formed the thinner part as soon as that parthas stiffened sufficiently to hold its shape, relieving the mouldingpres sure on the thicker part so that no harmful stresses are induced inthe stiffened thinner part byfiuid pressure exerted by the thicker part,subsequently withdrawinglpressure from the thicker part when the thickerpart "has stiffened sufficiently to hold its shapdfiandthen separatingthe moulded article from the mould.

According to another aspect of the invention-there 1 is provided amethod ofmouldingua' glass article comprising a central hollow part anda contiguous spread part, the hollow parthav-ing a wall which is thinnerthan the spread part, consisting in charging a mould with a requisitequantity of molten glass,- applying moulding pressure centrally to theglass to mould the hollow part then applying mouldingpressure to thesurrounding part 3,185,558 Patented May 25, 19165 central mouldingpressure as soon as the hollow part has stiffened sufficiently to holdits shape, relieving the surrounding moulding pressure so that noharmful stresses are induced in the stiffened hollow part by the spreadpart, subsequently Withdrawing the surrounding pressure from the spreadpart when the spread part has stiffened sufiiciently to hold its shape,and then separating the molded article from the mould.

The invention also comprehends apparatus for moulding a hollow glassarticle comprising two contiguous inner and outer parts one of which isthin relative to the other, including a hollow mould portion arranged toreceive a requisite quantity of molten glass, a first pressure memberand a complementary pressure member in sliding contact with said firstmember, said pressure members being relatively movable first to closethe mould and then to be withdrawn therefrom, and actuating means forthe pressure members whereby the first member leads the complementarymember on entering the mould, the first member is withdrawn after adwell sufficient to allow the thinner part of the article to stiffensufliciently to hold its shape while the complementary member remains inmoulding position until the thicker part has articles, and

stiffened sufficiently to hold its shape, and the pressure members arethen wholly withdrawn to permit access to the moulded article.

Further, the invention comprehends apparatus for tivelymovable in anaxial direction first to close the mould and then to be withdrawntherefirom, and actuating means [for the pressure members whereby theaxial member leads the concentric member on entering the mould and theaxial member is withdrawn after a dwell sufiicient to allow the hollowpart to stiffen sufficiently to hold its shape, while the concentricmember remains in moulding position until the spread area has stiffenedsufficiently to hold its shape, and the pressure members are then whollywithdrawn to permit access to the moulded article. i

The invention also comprehends a hollow glass article comprising twocontiguous inner and outer parts one of whichis thin relative to theother moulded by the method set out above. For example the'hollow glassarticle may be a glass insulator having a hollow head and a contiguousskirt extending radially from the head, the head having a wall which isthin relative to the skirt.

In order that the invention may be clearly understood an embodimentthereof will now be described by way of example'with reference to theaccompanying drawings in which: 7 FIGURE 1 is an elevation partly insection of apparatus accordingto the invention for moulding hollow glassFIGURES 2 to 5 respectively illustrate stages in a moulding operationusing the apparatus of FIGURE 1.

" Referring to FIGURE 1 of the drawings a method ac cording to theinvention of moulding a hollow glass artiof the glass tomould the spreadpart, withdrawing the Co-operating with the hollow mould portion 1 todefine the desired mould cavity are an axial pressure member 3 and acomplementary concentric pressure member 4, both of which are co-axialwith the central axis about which the hollow mould portion 1 issymmetrical. The mould portion 1 is rigidly supported by the base 5 ofthe moulding press, and the frame 6 of the moulding press is rigidlyfixed to the base 5.

The axial and concentric pressure members 3 and 4 are supported from anupper member 7 of the moulding press frame by actuating means whichincludes a main cylinder 8 which is fixed to the upper member 7, and anauxiliary cylinder 9. Both the main cylinder 8 and the auxiliarycylinder 9 are co-axial with the central axis of the hollow mouldportion 1.

A double-acting piston 10 is slidable in the main cylinder 8 and isconnected by a main piston rod 11 to a top cover plate 12 of theauxiliary cylinder 9. The main piston rod 11 passes through a gland 13at the bottom of the main cylinder 8. The main cylinder 8 has an upperport 14 and a lower port 15, and the ports 14 and 15 are respectivelyconnected by pressure lines 16 and 17 to a main two-way valve 18 whoseinput is connected to a pressure supply line 19. Similarly the auxiliarycylinder has an upper port 20 and a lower port 21, and the ports 20 and21 are respectively connected by pressure lines 22 and 23 to anauxiliary two-way valve 24, the input to which is also connected to thesupply line 19.

A double-acting piston 25 is slidable in the auxiliary cylinder 9 and isconnected by an auxiliary piston rod 26 to one end of a coupling memberor adaptor 27, the other end of which is fixed to a plate 28. Theauxiliary piston rod 26 passes through a gland 29 at the bottom of theauxiliary cylinder 9. The axial pressure member 3 is fixed to theunderside of the plate 28 and extends downwardly therefrom. Coolingchannels 30 are provided in the axial pressure member 3 for coolingpurposes and cooling fluid is supplied to these channels through thecoupling member or adaptor 27 by supply pipes 31.

The complementary concentric pressure member 4 is connected by ourvertical rods 32 which extend downwardly from the edges of an annularplate 33, which is fixed to the bottom of the auxiliary cylinder 9. Therods 32 pass through holes in the plate 28 and their lower ends arefixed to the cover plate 34 of the pressure member 4. As shown at 35 theconcentric pressure member 4 is in sliding contact with the axial member3.

Four vertical stop members consisting of bolts 36, one of which isshown, are fixed to the top of the concentric member 4 and pass throughholes in the plate 28. Each of the bolts 36 has an upper stop consistingof its head 37 and is threaded into the top of the concentric member 4and locked at any desired position by the lock-nut 38. The head 37limits the upward movement of the axial member 3 relative to theconcentric member 4. Four threaded stop members 39, one of which isshown, are fixed in' the plate 23 through which they pass and aresecured by nuts 40' on each side of the plate 28 so that the extent towhich they project downwards below the plate 28 may be adjusted andlocked. These four stop members 39 limit the downward movement of theaxial member 3 relative to the concentric member 4. The plate 28 alsocarries four threaded, adjustable stems 41 spaced symmetrically aroundits edge. Each of the stems 41 has an abutment 42 formed on its lowerend. One of the stems 40 is shown. The abutments 42 are arranged to abuta ring-plate 43 of the mould, which rests upon the hollow mould portion1, when the axial pressure member 3 has been moved downwardly to itsmoulding position.

In FIGURE 1 the axial and concentric pressure members 3 and 4 are shownwithdrawn away from the mould portion 1. In this initial position themain piston 10 is located in its uppermost position in the main cylinder8 and the auxiliary piston 25 is located in the lowest position in theauxiliary cylinder 9 to which the stop members 39 allow it to descendaccording to the required extension of the axial member 3 through theconcentric member 4. A complete moulding operation for moulding ahighvoltage insulator will now be described.

The hollow mould portion 1 is first charged with a requisite quantity ofmolten glass 2. In order to bring the pressure members 3 and 4 intotheir initial positions as shown in FIGURE 1, the auxiliary valve 24 isoperated to admit air under pressure along line 22 through port 20 tothe top of the auxiliary cylinder 9 and the piston 25 descends andcauses the axial member 3 to extend through the concentric members 4 asfar as the stop members 39 allow. Then the main valve 18 is operated toadmit air under pressure along line 16 through port 14 to the top of themain cylinder 8 and the piston 10 descends and moves both the axialmember 3 and the concentric member 4 downwardly towards the hollow mouldportion 1.

The now fully extended axial member 3 leads the concentric member 4 onentering the mould and displaces the molten glass until the abutments 42abut the ringplate 43 on the mould portion 1 as shown in FIGURE 2, andthe hollow head of the insulator is shaped in the thinner part 44 of themould cavity. The thickness of this part 44 of the mould cavity isdetermined by the operative length of the stems 41 which length isadjustable. When the abutments 42 abut the ring-plate 43 no furtherpressure is exerted on the glass in the mould by the axial member 3although air under pressure is forcing the piston 25 in a downwarddirection.

After the axial member 3 has been arrested, the concentric member 4continues to move relatively to the axial member 3 from the positionshown in FIGURE 2, in which a part of the concentric member 4 is alreadytouching the molten glass 2, to the position shown in FIGURE 3, that isuntil the molten glass 2 completely fills the mould cavity and arrestsfurther movement of the concentric member 4. The mould is thencompletely closed and the skirt of the insulator is shaped in thethicker part 45 of the mould cavity.

As stated above, when the axial member 3 enters the molten glass 2 itshapes the central thin hollow part of the insulator, displacing somemolten glass outwardly into the thicker part 45 of the mould cavity. Theconcentric member 4 then descends and shapes the spread thicker part orskirt of the insulator. The central thin hollow part of the insulator,which is in contact with the cooled axial member 3, is rapidlystifiening and will become too stilt to contract without breaking aroundthe axial member 3, which is becoming hotter in contact with the hotglass and is therefore expanding. Accordingly as soon as the concentricmember 4 has shaped the skirt of the insulator and the thinner hollowpart has stifiened suificiently to hold its shape the axial member 3 iswithdrawn by operating the auxiliary two-way valve 24 to admit air underpressure through the pressure line 23 and the port 21; and at the sametime the main two-way valve 18 is closed so that, although theconcentric member 4 is still held in moulding position on the skirt ofthe insulator, the pressure on the skirt is relieved in order that thestill mobile glass in the skirt shall not exert any fluid pressure uponthe central thin hollow part of the insulator.

Any tendency of the moulded insulator to crack is thus prevented byfulfilling the conditions imposed by the fact that, because the timetaken by the thinner central hollow head of the insulator to stififensufiiciently to hold its shape is shorter than that required by thethicker spread skirt of the insulator to stilfen sufficiently to holdits shape, their respective pressure members must be maintained in theirmoulding position for different times.

If the axial member 3 and the concentric member 4 were both allowed todwell in the position shown in FIG URE 3 for the same length of timebefore being withdrawn, the moulded insulator would either be cracked orwould not be properly formed. A combined dwell for a time long enough toallow the thicker skirt to stilfen sufiiciently to hold its shape wouldbe too long for the thinner hollow head, which would crack. Also if thecombined dwell were only long enough to allow the hollow head to stiffensufiiciently to hold its shape, the thicker skirt would not stiffensufficiently before the pressure members are withdrawn and would run outof shape. Accordingly the axial member 3 is withdrawn after a dwellsuhicient to allow the hollow head of the insulator to stiliensufficiently to hold its shape, and the concentric member 4 remains informing position until the spread skirt has stifiiened suificientiy tohold its shape.

When, in order to withdraw the axial member 3, air under pressure isadmitted to the lower end of the auxiliary cylinder 9 the piston 25rises in the cylinder 9 only until the top face of the plate 28 abutsthe head 37 on the bolt 36 as shown in FIGURE 4. The piston 25 is thenin its uppermost position in the cylinder 9. While the axial member 3 isbeing withdrawn by this small distance the concentric member 4 remainsin its moulding position, although without applied force, and the member4 remains in this forming position until the spread skirt is set up. Themain Valve 18 is then operated to admit air under pressure to the lowerpart of the main cylinder 8 through the line 17 and the port 15 so thatthe concentric member 4 is withdrawn from the mould portion 1. Movementof the piston up the cylinder 8 continues until the pressure members arewholly withdrawn to the position shown in FIGURE 5, and access is thenpermitted to the moulded high-voltage insulator 46, which is thenseparated from the lower hollow mould portion 1.

It will be understood that, although the method has been describedherein with reference to the manufacture of a moulded glass high-voltageinsulator, this method can also be applied to the manufacture of otherglass arti cles, such as for example, a cathode-ray tube which has acentral hollow part, or neck, and a contiguous spread part which formsthe flared walls of the cathode-ray tube extending away from the necktowards the face of the cathode-ray tube and of greater thickness thanthe neck.

Although the actuating means has been described as being supplied withair under pressure, it will be understood that any other suitableworking fluid may be used in place of air, for example a liquid. Themain valve 18 and auxiliary valve 24 may be adjustable manually or, ifthe method is to be carried out automatically, by control members whichwill operate the valves at the appropriate times in the moulding of anarticle.

I claim:

1. A method of pressure moulding a hollow glass article comprising twocontiguous inner and outer parts one of which is thinner than the other,consisting in charging a mould with a requisite quantity of moltenglass, applying downward moulding pressure to the glass to mould theinner part, then applying downward moulding pressure to mould the outerpart, withdrawing the moulding pressure which has formed the thinnerpart as soon as that part has stiffened sufliciently to hold its shape,while simultaneously relieving the moulding pressure on the thicker partso that no harmful stresses are induced in the stiffened thinner part byfiuid pressure exerted by the thicker part, subsequently withdrawingpressure from the thicker part when the'thicker part'has stiffenedsufficiently to hold its shape, and then separating the moulded articlefrom the mould.

2. A method of pressure moulding a glass insulator comprising a centralhollow head and a contiguous spread skirt, the hollow he-ad having awall which is thinner than the skirt consisting in charging a mould witha requisite quantity of molten glass, applying downward mouldingpressure centrally to the glass to mould the hollow head, then applyingdownward moulding pressure to the surrounding part of the glass to mouldthe skirt, withdrawing the central moulding pressure as soon as thehollow head has stiffened sufliciently to hold its shape whilesimultaneously relieving the surrounding moulding pressure so that noharmful stresses are induced in the stiffened hollow head by the skirt,subsequently withdrawing the surrounding pressure from the skirt whenthe skirt has stiffened sufficiently to hold its shape, and thenseparating the moulded insulator from the mould.

References Cited by the Examiner UNITED STATES PATENTS 791,410 5/05Fetters -311 1,030,252 6/ 12 Burleigh 65-314 1,340,366 5/20 Bingham65-318 1,578,448 3/26 Lebby 65-68 1,812,565 6/31 Sloan 65-72 2,011,9808/35 Miller 65-314 2,3 24,149 7/ 43 Gray 65-305 2,572,511 10/51Palmquist 65-71 2,843,973 7/5 8 Clignet 65-248 2,861,394 11/58 Rufi?65-71 3,005,122 10/61 Coleman et a1 65-305 DONALL H. SYLVESTER, PrimaryExaminer.

BENJAMIN BENDETT, ARTHUR P. KENT, MORRIS O. W OLK, Examiners.

1. A METHOD OF PRESSURE MOULDING A HOLLOW GLASS ARTICLE COMPRISING TWOCONTIGUOUS INNER AND OUTER PARTS ONE OF WHICH IS THINNER THAN THE OTHER,CONSISTING IN CHARGING A MOULD WITH A REQUISITE QUANTITY OF MOLTENGLASS, APPLYING DOWNWARD MOULDING PRESSURE TO THE GLASS TO MOULD THEINNER PART, THEN APPLYING DOWNWARD MOULDING PRESSURE TO MOULD THE OUTERPART, WITHDRAWING THE MOULDING PRESSURE WHICH HAS FORMED THE THINNERPART AS SOON AS THAT PART HAS STIFFENED SUFFICIENTLY TO HOLD ITS SHAPE,WHILE SIMULTANEOUSLY RELIEVING THE MOULDING PRESSURE ON THE THICKER PARTSO THAT NO HARMFUL STRESSES ARE INDUCED IN THE STIFFENED THINNNER PARTBY FLUID PRESSURE EXERTED BY THE THICKER PART, SUBSEQUENTLY WITHDRAWINGPRESSURE FROM THE THICKER PART WHEN THE THICKER PART HAS STIFFENEDSUFFICIENTLY TO HOLD ITS SHAPE, AND THEN SEPARATING THE MOULDED ARTICLEFROM THE MOULD.